Glenn - Voice Actor

I know this is not an actual issue but it is an interesting side note seeing as Steven Yeun plays Glenn in the show and the characters look exactly alike for the most part but yet in the end credits I noticed that Glenn was played by someone else. Any given reason other than availability?

And besides that the game is based on the comic books and not the TV show so it should have no relation to it be it in the form of music, or actors or anything else that only exists with the show. The fact that the character looks like the actor is probably coincidental (though I don't really see it myself, but then I've not played it yet) and maybe even a little bit racist.